Function Naming And Execution

Hi,

I am converting a database from Oracle to SQL-Server 2005 and in that context I needed to implement a function in the database. My database default uses the dbo schema and the function is there too. I define a function called "Translate" and wanted to use it like this :

SELECT translate(Phonenumber, '0123456789 ()+-', '0123456789') as PhonenumberFROM Customer

but what pussled my was that in order to make this work I had to prefix the translate method with "dbo." like this :

SELECT
dbo.translate(Phonenumber, '0123456789 ()+-', '0123456789') as Phonenumber
FROM
Customer

as all "objects" I'm using resides in the dbo schema - why must I prefiks only the function and not the table????